1. Field of the Invention
This invention relates generally to electrical flashers and, in particular, flashers suitable for directional lights of a motor vehicle. More particularly, this invention relates to a combination turn signal-hazard warning flasher that allows for the use of a simple hazard warning switch in vehicles having three turn signal lamps per side for hazard warning operation.
2. Description of the Prior Art
Turn signal and hazard warning flashers are electronic devices that are used in cars to cause the turn signal lamps to blink on and off. Representative flasher units known in the art are those disclosed in U.S. Pat. No. 3,824,542, issued to Schorter, and U.S. Pat. No. 4,173,013, issued to Spiteri.
Flashers are also critical safety components of cars, used to indicate to other drivers whether a vehicle is turning, or disabled. The Federal Government has accordingly developed safety standards that flashers are required to meet. Since flashers are mass produced for millions of cars, a savings in cost and improvement in safety or performance such as provided in the present invention can result in a flasher that is of a distinct advantage to a manufacturer, and can save lives of motorists who use them.
The Federal motor vehicle safety standard (FMVSS) 108 requires all vehicles at the time of their manufacture to include a device for indicating to the driver a failure of one or more turn signal lamps in accordance with Society of Automotive Engineers (SAE) Standard J588e. An exception to this requirement exists for vehicles 80 or more inches in overall width, trucks that are capable of accommodating a slide-in camper, or vehicles equipped to tow trailers. With one or more lamps in "failure mode" (burned out, physically damaged or otherwise inoperative), SAE Standard J588e specifies that a lamp outage signal can be indicated by operating the lamps at a failure rate, for example, in "steady on", "steady off", or by a significant change in the flashing rate of the illuminated indicator. FMVSS-108 also requires that the vehicle hazard warning system continue to flash at the specified normal flash rate over lamp loads from 2 turn signal lamps to twice the turn signal lamp load.
Vehicles lamp systems can be classified as follows: 2 lamp turn signal systems have 1 front and 1 rear turn signal lamps on each side of the vehicle; 3 lamp turn signal systems have 1 front and 2 rear turn signal lamps on each side of the vehicle. For hazard warning, a 4 lamp hazard warning system has 2 front and 2 rear turn signal lamps that flash in hazard warning; a 6 lamp hazard warning system has 2 front and 4 rear turn signal lamps that flash in hazard warning. In vehicles having a 2 lamp turn signal system, and a 4 lamp hazard warning system, the use of a combination turn signal-hazard warning flasher requires no additional or special wiring, as the flasher input and output terminals are common to both systems. This flasher provides the specified flash rate over the lamp load range of 2 to 4 lamps, 2 lamp turn signal load and from 2 to 4 lamps hazard warning load, while providing means to indicate failure at 1 turn signal lamp.
A shortcoming of the prior art is that in vehicles having a 3 lamp turn signal system and a 6 lamp hazard warning system, a common practice is for the flasher to have an additional load carrying terminal, at either input or output of the flasher, and for the hazard warning switch to have an added set of switching contacts. These additions are required in order to change the internal operating characteristics of the flasher, thereby providing the means to indicate failure of one or more turn signal lamps, while providing the specified normal flash rate down to 2 lamps in hazard warning.